Is there a minimum contract period or commitment?

No. None of the plans have a minimum contract period. You can cancel whenever you want, with just one click from your profile, and you will keep full access until the end of the period you have already paid for. There is no penalty or cancellation fee.

And your progress is never lost. If you cancel, your account reverts to the free plan: you keep your completed levels, your speed, your stats, and your achievements, and you still have access to levels 1 to 7. If you come back later, you pick up right where you left off.